The incidence of coronary artery anomalies in a routine coronary angiography series is between 0.5% and 1.0%.1)2) Intercoronary communication is a rare coronary artery anomaly with unidirectional or bidirectional blood flow between two coronary arteries. Yamanaka and Hobbs2) reported the incidence of intercoronary connections to be 0.002% in a study comprising 126595 patients. It is suggested that a defective embryological development allowed the existing intercoronary channel to remain prominent.3-5)

A 45-year-old male presented with chest pain that was aggravated in early morning. He was a current smoker with 20 pack-years and used to have chest pain on exertion intermittently. Electrocardiogram showed ST elevation on leads from V 1-3, and chest X-ray was normal. Laboratory findings revealed mildly elevated cardiac enzyme; creatine kinase-MB and troponin I level were 6.9 ng/mL (0.0-5.0) and 0.3 ng/mL (0.00-0.16), respectively. Transthoracic echocardiography demonstrated hypokinetic mid anteroseptum with preserved left ventricular global systolic function. Coronary angiography was performed and revealed no significant luminal narrowing or occlusion of coronary arteries. However, selective injection of left coronary artery showed retrograde filling of the distal right coronary artery (RCA) from distal left circumflex artery (LCX), and right coronary injection visualized RCA and distal and mid portion of LCX simultaneously visualized (Fig. 1). Retrograde filling was not related to collaterals, but to a bidirectional intercoronary communication.

When ergonovine was administered intravenously in a dose of 50 ug, the significant spasm of proximal left anterior descending artery (LAD) was provoked with chest pain (Fig. 2A). The spasm and chest pain subsided promptly after intracoronary injection of 200 ug of nitroglycerin (Fig. 2B).

Intercoronary communications are rarely seen during coronary angiography in patients with and without coronary artery narrowing. They are distinguished from coronary collaterals that are seen in the patients with occlusive coronary artery disease by angiographic features and histological structure. Intercoronary arterial communications are single, extramural, straight and larger in diameter (>1 mm) compared to collaterals. The histological structure of the connecting vessel has the characteristics of a normal arterial wall, with a well defined muscular layer.6) Two types have been reported, which are a communication between LAD and posterior descending artery in the distal interventricular groove, and a communication between LCX and RCA in the posterior atrioventricular groove, as shown in our case.4)

The predominant symptom at presentation is chest pain, which is usually atypical, and non-invasive diagnostic procedures have often doubtful results.4)7) There are controversies regarding functional significance of intercoronary connections. Sometimes, these connections may play a protective role for myocardium, if the coronary artery obstruction has developed in one of the two connecting vessels.4)8) On the other hand, myocardial ischemia can be resulted from a coronary steal by the unidirectional intercoronary communication.5)9)

Our case presented bidirectional intercoronary communication having coronary spasm on provocation test without significant coronary narrowing. Takatsu et al.10) reported similar cases of intercoronary communications with vasospastic angina. They proposed the intercoronary communications were useful in at least partially protecting myocardium from ischemia during spasm. Whereas spastic coronary artery was related to the intercoronary connections in their report, it was not directly related to intercoronary communication in our case. Although the relation between intercoronary connection and coronary artery spasm is not clear, consideration of provocation for coronary vasospasm can be useful if intercoronary communication without significant coronary obstruction is found in patients with chest pain.